This invention relates generally to drainage systems and more particularly to a temperature actuated drain system that can be used for draining pooled water from roofs.
A drain system of this general type is shown in U.S. Pat. No. 4,059,126, the disclosure thereof being incorporated herein by reference. The apparatus therein described utilizes a chamber which allows solar heat to penetrate into the chamber when the sun is shining and impinge upon a heat-absorbing plate within the chamber. The heated plate, in turn, causes the air within the chamber to be heated and, as a consequence, to expand. A pressure-responsive one-way valve allows expanding air to escape from the chamber until the pressure within the chamber equals that outside the chamber. When clouds shield the chamber from the sun or when the sun sets at night, the air within the chamber cools. A subatmospheric pressure is created within the chamber. Air is drawn through a tube and through a second pressure-responsive one-way valve into the chamber to return the pressure within the chamber to the ambient pressure outside of the chamber. The distal end of the tube is connected to a siphon having an inlet end immersed in a pool of water to be drained and an outlet end fitted with a third pressure-responsive one-way valve positioned at a level below the inlet end of the siphon. The solar actuated pumping action is continued until sufficient water is pulled into the siphon to cause the one-way valve at the discharge end of the siphon to open. Water will continue to be drawn into the siphon from the pool and expelled from the siphon until the pool is drained sufficiently that the inlet end of the siphon is no longer immersed in water.
An improved single valve drain system is shown in U.S. Pat. No. 4,168,717, the disclosure thereof being incorporated herein by reference. In the improved system, a chamber similar to the chamber of the above-described drain system is in continuous open communication with a siphon having an inlet end immersed in a pool of water to be drained and a discharge end fitted with a pressure-responsive one-way valve positioned at a level below the inlet end of the siphon. A pumping action of the type described above, except that expanding air is expelled through the one-way valve at the discharge end of the siphon, causes water to be pulled into the siphon until a sufficient weight of water is contained at the discharge end of the siphon tube to cause the one-way valve to open. Water will continue to be pulled from the pool, into the siphon and expelled from the siphon until the inlet end of the siphon is no longer immersed in water.